Quantum Back-Action of an Individual Variable-Strength Measurement
Abstract
Measuring a quantum system can randomly perturb its state. The strength and nature of this back-action depend on the quantity that is measured. In a partial measurement performed by an ideal apparatus, quantum physics predicts that the system remains in a pure state whose evolution can be tracked perfectly from the measurement record. We demonstrated this property using a superconducting qubit dispersively coupled to a cavity traversed by a microwave signal. The back-action on the qubit state of a single measurement of both signal quadratures was observed and shown to produce a stochastic operation whose action is determined by the measurement result. This accurate monitoring of a qubit state is an essential prerequisite for measurement-based feedback control of quantum systems.
- Publication:
-
Science
- Pub Date:
- January 2013
- DOI:
- 10.1126/science.1226897
- arXiv:
- arXiv:1903.11732
- Bibcode:
- 2013Sci...339..178H
- Keywords:
-
- PHYSICS;
- Quantum Physics
- E-Print:
- Science 11 Jan 2013: Vol. 339, Issue 6116, pp. 178-181